Nanometer-sized dendrite-like structures with a designed element, W, is fabricated on an insulator substrate, Al2O3, with an electron-beam-induced decomposition (EBID) in a transmission electron microscope (TEM). The fabricated structures are characterized with convention and high resolution TEM. The dendritic structure with tips in about 3 nm grows radially at convex surface of a substrate. The bcc structural W crystal grains in nanometers are composed in the dendrites. A mechanism is proposed to explain the growth and morphology of the deposit involving a charge-up on surface, a movement to and an accumulation of charges at convex surface or tips of substrate or the branched deposit. (C) 2004 Elsevier B.V. All rights reserved.